Try this:
<?php
$loc = @array_values(array_filter(array(osc_search_city(), osc_search_region(), osc_search_country())))[0];
$cat = (isset($category['s_name']) ? $category['s_name'] : '');
$tit = implode(', ', array_filter(array($cat, $loc)));
if(osc_search_total_items() <= 0) {
if($tit != '') {
echo sprintf(__('No listings found in %s', 'delta'), $tit);
} else {
echo __('No listings found', 'delta');
}
} elseif($tit != '') {
echo sprintf(__('%s results found in %s', 'delta'), osc_search_total_items(), $tit);
} else {
echo sprintf(__('%s results found', 'delta'), osc_search_total_items());
}
?>